Method for preparing oriented polymer structures and said structures

ABSTRACT

A system for preparing oriented block copolymer structures includes a copolymer solution, a device capable of providing a flow field and an evaporation device. The device can be at least two cylinders that are parallel and adjacent to one another to form a nip and a driving mechanism to rotate each cylinder. Means for controlling a solvent environment and evaporation are provided. A method for preparing oriented block copolymer structures includes providing at least two cylinders which are parallel and adjacent to one another so as to form at least one nip, rotating each of the cylinders such that at the nip the cylinder surfaces are moving in the same direction with substantially the same or different tangential velocity, introducing a block copolymer solution into one of the nips of the rotating cylinders, thereby subjecting the polymer solution to a flow field and whereby orientation of the solution begins and evaporating the solvent from the block copolymer solution, whereby ordered microphase separation occurs and the oriented block copolymer structure is formed on the surface of at least one cylinder.

The United States Government retains rights to this invention by virtueof research finding by the United States Air Force under GrantASOSR-90-0150.

This application is a continuing application of U.S. application Ser.No. 08/168,791, filed Dec. 8, 1993, now U.S. Pat. No. 5,622,668, whichis a division of U.S. application Ser. No. 07/832,469, filed Feb. 7,1992, abandoned.

BACKGROUND OF THE INVENTION

This invention relates to microphage orientation of block copolymers.The invention further relates to an apparatus and method for theorientation of block copolymer structures.

Block copolymers are macromolecules composed of segments of differentcovalently bonded homopolymers. At equilibrium, block copolymerssegregate into microdomains consisting of primarily one homopolymer withcovalent bonds to the second homopolymer of the block copolymer existingat the interfaces. These microdomains have a local orientation resultingin local anisotropy of the material. Improved macroscopic orientation ofthese domains would impart anisotropic mechanical, magnetic, electricaland optical properties to the block copolymer. The improved propertiessuggest applications in optical wave guides and uses as membranes andlaminates.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a system forpreparing block copolymer structures with aligned microdomains with ahigh degree of order. It is further an object of the present inventionto provide a method for preparing block copolymer structures of nearsingle crystal quality.

In one aspect of the invention, a system is provided for preparingoriented microphase-separated block copolymer. The system includes ablock copolymer solution, a device capable of providing a flow field forthe block copolymer solution, thereby subjecting the copolymer solutionto fields of shear and/or elongation and/or compression which start theorientation of the polymer in solution. An evaporation device isprovided for evaporation of the solvent whereby ordered microphaseseparation occurs and the oriented copolymer structure is formed.

In a preferred embodiment, the device adapted to provide a flow fieldincludes at least two cylinders that are parallel and adjacent to oneanother so as to form at least one nip and a driving mechanism forrotating each cylinder such that the cylinder surfaces at the nip aremoving in the same direction with the same or different tangentialvelocity. The copolymer solution flows continuously between the rotatingcylinders thereby creating a flow field which begins the orientation ofthe copolymer. Upon evaporation of the solvent, microphase separationoccurs and an oriented block copolymer film is deposited on at least onecylinder. This particular embodiment is referred to hereinafter as the"adjacent cylinders" system.

In another embodiment of the adjacent cylinders system, a multiplicityof cylinders are arranged around a central cylinder such that thecentral cylinder forms a nip with each cylinder at intervals around thecircumference of the central cylinder. The film is formed on the centralcylinder by using cylinders coated with or made from a high releasematerial for the peripheral cylinders.

In yet another preferred embodiment, the device adapted to provide aflow field includes an inner cylinder and an outer cylinder and adriving mechanism for rotating at least one cylinder. The cylinders areeccentric and the inner cylinder is located parallel to and in theinterior of the outer cylinder, such that the outer surface of the innercylinder approaches the inner surface of said outer cylinder and suchthat the surfaces of the cylinders at the point of closest approach aremoving in the same direction and with the same or similar tangentialvelocity. A driving mechanism rotates at least one of the cylinders. Ina preferred embodiment, at least one cylinder is independently drivenand cylinders communicating with the rotating cylinder are themselvesput into motion. Preferably the outer cylinder is mechanism-driven,while the inner cylinder rotates by communication with the outercylinder. In another preferred embodiment, the inner cylinder may alsobe independently driven by an external mechanism. The copolymer solutionflows continuously between the rotating cylinders at said nip therebycreating a flow field. Upon evaporation of the solvent, microphaseseparation occurs and an oriented block copolymer film is deposited onat least one cylinder. This particular embodiment of the invention isreferred to hereinafter as the "eccentric cylinders" system.

The device for rotating the cylinders can be any conventional drivingmechanism, such as an electric motor. It will be recognized by thoseskilled in the art that other means of driving the cylinders arepossible and within the scope of the present invention.

In the eccentric cylinders system described immediately above, the nipgap is initially essentially zero and is finally the thickness of theoriented layer. The nip gap is affected by a number of factors, such as,the viscosity of the polymer solution, the thickness of the finalstructure and the strength of the flow field. In the adjacent cylinderssystems, the nip gap can be set to any desired value and can also bevaried during operation.

The cylinders of the adjacent cylinders system are not required to be ofthe same diameter. The diameter of the cylinders can be selected toobtain a desired flow field. A preferred flow field will be obtained forcylinders of substantially equal diameter. The relative sizes of the twocylinders forming a nip will affect the residence time of the copolymersolution and the contact angle and area of the copolymer solution in thenip area.

The eccentric cylinders system is required to have a smaller innercylinder. Preferably, the diameter of the inner cylinder is in the rangeof 30 to 90 percent of the diameter of the outer cylinder, The relativesizes of the two cylinders forming the nip will affect the residencetime of the copolymer solution and the contact angle and area of thecopolymer solution in the nip area.

The cylinders of both the adjacent cylinders and eccentric cylinderssystems are rotted at a measurable tangential velocity. The tangentialvelocity may be varied during use. For example, as the flowing solutionbecomes more viscous and relaxes at a slower rate, the tangentialvelocity can be decreased. An important factor in determining theoptimal tangential velocity is the ratio of the tangential velocity tothe relaxation rate of the copolymer. The time elapsed betweensuccessive passages of the copolymer through the nip should not besufficient to allow relaxation (and possible disordering) of thecopolymer. The optimal tangential velocity is a function of therelaxation rate of the polymer, the residence time of the polymersolution in the nip area and the strength of the flow field.

The cylinders used in preferred embodiments are prepared fromconventional materials that are inert with respect to the copolymersolutions. A partial list of acceptable materials includes stainlesssteel and aluminum. In another preferred embodiment of the invention, atleast one of the cylinders is made from or coated with a high releasematerial, such as polytetrafluoroethylene. This prevents the copolymersolution and the resultant oriented film from sticking to the cylinder.In another preferred embodiment, at least one cylinder is coated with amaterial that interacts with at least one of the copolymer blocks. Thematerial can be, for example, a polar surface that will interactpreferentially with the polar block of the copolymer.

The evaporation device can be any conventional apparatus used for theevaporation of solvents. In a preferred embodiment of the invention, theevaporation device can include a gas flow field which passes over thecylinder surfaces. Conventional methods of creating a gas flow field arewithin the scope of the invention. These include, but in no way arelimited to air knives, air jets and ventilation systems. The gas flowfield can be parallel or perpendicular to the cylinder axes. Theevaporation device can further include a chamber surrounding therotating cylinders and a vacuum apparatus capable of lowering thechamber pressure below atmospheric pressure.

In another preferred embodiment of the invention, means of providing acontrolled solvent environment over the cylinders is provided. Such adevice could be a container surrounding the system and communicatingwith a solvent reservoir. The temperature of the solvent can also becontrolled to promote controlled solvent evaporation. In anotherpreferred embodiment of the invention, a heater is provided capable ofheating the surfaces of the cylinders. The cylinders can be heated atdifferent points in the operation of the system to promote controlledsolvent evaporation.

In another aspect of the present invention, a method for preparingoriented block copolymer structures includes providing at least twocylinders which are parallel and adjacent to one another so as to format least one nip, rotating each of the cylinders such that at the nipthe cylinder surfaces are moving in the same direction withsubstantially the same or different tangential velocity, introducing ablock copolymer solution into one of the nips of the rotating cylinders,thereby subjecting the polymer solution to a flow field and wherebyorientation of the solution begins and evaporating the solvent from theblock copolymer solution, whereby ordered microphase separation occursand the oriented block copolymer structure is formed on the surface ofat least one cylinder. The block copolymer can be any diblock, triblockor multiblock copolymer. The solution can additionally containhomopolymer(s). The solvent can be a solvent mixture, a non-preferentialsolvent or a preferential solvent. In some embodiments, anon-preferential solvent is preferred. By non-preferential solvent, itis meant that the solvent has no preferred affinity for eitherhomopolymer segment of the block copolymer.

In a preferred embodiment, the factors determining the optimaltangential velocity of the cylinders at the nip comprise the relaxationrate of the polymer, the residence time of the polymer solution in thenip area and the strength of the flow field.

In preferred embodiments, a second block copolymer solution is appliedto the cylinders after the first block copolymer solution has beencoated onto a cylinder as an oriented copolymer structure. The secondcopolymer solution can be the same in composition as the first blockcopolymer solution, resulting in a thicker structure of uniformcomposition. Alternately, the second block copolymer solution can be ofa different composition. Treatment of the first block copolymer film toset or cross-link the block copolymer film is possible to preventredissolution of the copolymer film upon application of the second blockcopolymer solution. Such treatment includes ultraviolet irradiation,electron beam irradiation and chemical crosslinking.

BRIEF DESCRIPTION OF THE DRAWING

In the Drawing:

FIG. 1 is a cross-sectional view of an apparatus according to onepreferred embodiment of the invention;

FIG. 2 is a cross-sectional view of an apparatus according to a secondpreferred embodiment of the invention;

FIG. 3 is a cross-sectional view of an apparatus according to a thirdpreferred embodiment of the invention;

FIG. 4 is a schematic representation of (a) the nip region in aroll-casting apparatus as shown in FIG. 3 and (b) the nip region in aroll-casting apparatus as shown in FIG. 1;

FIG. 5 is a 2-D small angle X-ray scattering (SAXS) pattern of aroll-cast film in which the path of the X-ray was parallel to theorientation of the polystyrene cylinders; and

FIG. 6 is a transmission electron microscopy (TEM) photomicrograph of amicrophase separated block copolymer prepared (a) according to the priorart and (b) according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

During microphase separation, block copolymers segregate intomicrodomains consisting of different homopolymer segments with chemicalbonds existing across the interfaces. By homopolymer, as that term isused here, it is meant a polymer consisting of one type of monomer unit.

The morphology formed during microphase separation depends upon themolecular weights of the homopolymer segments and the fraction of eachof the homopolymers in the overall system. When the fraction of eitherhomopolymer is far from 0.5, then the minority component tends to formdomains in a matrix composed of the majority component. The domainsrange from spheres at low fractions of the minority component throughcylinders to the ordered bicontinuous double-diamond structure (OBDD) athigher fractions of the minority component. At even higher fractions forwhich the amount of both components is comparable, a lamellar structureis formed. The typical size of the microdomains is on the order ofseveral hundred Angstroms, which in turn may assemble in grains reachingon the order of microns.

Grains composed of cylindrical or of lamellar microdomains have a localpreferred orientation resulting in local anisotropy of the material.Since these grains are relatively small in comparison to the dimensionsof the whole sample and since they are often in a random distribution,the resultant macroscopic sample usually displays isotropic properties.Diblock and triblock copolymers have been treated with the intention oforienting the microstructure on a larger scale and improving the overallanisotropy of the materials.

Previous attempts to orient or align block copolymers microdomainsinvolved mechanical deformation or application of an electrical field tothe material above the glass transition temperatures of all thecomponents, i.e., in a molten microphase-separated state. Above theglass transition temperature, the thermal motion of the polymer chainsincreases so that some reorientation of the polymer is possible. Thesetechniques resulted in improved alignment of the copolymermicrostructure. Orientation was improved by the reorientation ofpre-existing grains in the material. However, because the grains have a"memory" of their original position there is oftentimes a relaxation toa more disordered state. The present invention affords a microstructureof a single-crystal nature without grain boundaries and thereforeprovides oriented block copolymer structures with improved stability.

An electric field has also been successfully applied at elevatedtemperatures to orient a homogeneous copolymer material as it microphaseseparates. The orientation of lamellae parallel to the free surface insymetric diblock polymers has also been previously demonstrated.

The present invention provides macroscopic orientation of blockcopolymer structures with a marked improvement in the degree of orderover the prior art structures by flow of a concentrated polymer solutionat room temperature, i.e., above the microphase separation transition(MST) temperature of the solution. For the purposes of the presentinvention, any diblock, triblock or multiblock copolymer can be used.Any solvent with the appropriate solubility can be used. Furthermore,any block copolymer composition can be used although orientation ofspherical microdomains will be poor.

According to the invention, a block copolymer solution is placed in aflow field, thereby subjecting the solution to fields which forminitially aligned microdomains in solution. Any flow field sufficient toalign the copolymer and any means of achieving the flow field are withinthe scope of the invention.

A system according to one aspect of the invention for orientation ofblock copolymer microdomains is illustrated in FIG. 1. The system isreferred to hereinafter as a roll-casting system. The system 10 consistsof two adjacent and parallel cylinders 11 and 12 and is similar to theconventional set-up of calendars or roll-mills. The cylinders 11 and 12counter-rotate on axes 13 and 14, respectively, in the directionsindicated by arrows 15 so that a nip 18 is formed between them. Each ofthe cylinders 11 and 12 is independently powered by a driving mechanism(not shown). However, as the cylinders are not required to haveidentical diameters, they may be rotated at the appropriate angularvelocity in order to maintain substantially equal or differenttangential velocities at nip 18. A maximum flow field is obtained whenthe tangential velocities are comparable. A block copolymer solution 20is applied to the nip 18 of the rotating cylinders 11 and 12. Theevaporation device can include a gas flow field indicated by arrow 22over the surface of the cylinder 11 and 12. Alternately, the cylindersand solution can be housed in a chamber 24 which communicates with avacuum apparatus 26. One of the cylinders can be made from or coatedwith a high release material, such as polytetrafluoroethylene, toprevent adhesion of the film on that cylinder. FIG. 2 illustrates asystem 30 for another preferred embodiment of the invention where amultiplicity of cylinders are used. A central cylinder 31 is surroundedabout its circumference by peripheral cylinders 32. Each cylinder 32forms a nip 34 with the central cylinder 31. The peripheral cylinders 32are coated with or made from a high release material 36 so that theblock copolymer film 20 is formed preferentially on the central cylinder31. In the particular arrangement shown in FIG. 2, each completerotation of the central cylinder 31 subjects the block copolymersolution to four flow fields resulting in more efficient and rapidalignment of the block copolymer microdomains. FIG. 2 is not intended tolimit the system to just four peripheral cylinders and it is appreciatedthat any number of cylinders of equal or unequal diameter arecontemplated within the scope of the invention.

FIGS. 3a and 3b illustrate an eccentric cylinders system 40 fororientation of block copolymer structures. Referring to FIG. 3a. thesystem includes an inner cylinder 42 and an outer cylinder 44. Thecylinder 42 nests inside the cylinder 44, thereby forming a nip 46 atthe point of closest approach. The cylinders 42 and 44 co-rotate in thedirection indicated by arrows 47. A driving mechanism (not shown)communicates with cylinder 44. Cylinder 42 rotates by communication withthe outer cylinder 44 at the same or similar tangential speed. The innercylinder 42 can be a solid cylinder or filled with mercury to provideadded weight. The inner cylinder may be independently driven by anexternal mechanism (not shown). A block copolymer solution 20 isintroduced into the nip 46. An evaporation or controlled solvent devicesimilar to those illustrated in FIG. 1 can be used. As the solventevaporates, the concentration of the solution increases and a film isformed on both an inner side 48 of the outer cylinder 44 and an outerside 49 of the inner cylinder 44 (see FIG. 3b). It is apparent from thisdescription of the system 40 that the nip gap is not an independentvariable. The nip gap at nip 46 in FIG. 3a is essentially zero in theearly states of processing the polymer solution. The nip gap at nip 46in FIG. 3b is the thickness of the film at the late stages of processingthe polymer solution.

The usual setup of rotating roils in polymer processing is either ascalendars or as roll-mills. In both these cases polymer melt flowsbetween adjacent rolls, passing through a minimum gap called the nip andcoating one or both of the rolls. Gaskell ("The Calendaring of PlasticMaterials", J. Appl. Mech. 17, 334 (1950)), herein incorporated byreference, presented an analysis of the flow of plastic materialsbetween calendars of equal radii. Later Tadmor and Gogos ("Principles ofPolymer Processing", Wiley, New York, N.Y. (1979)), herein incorporatedby reference, rederived the expressions for the pressure and velocityprofiles of a plastic material in this flow field. A brief summary ofthe key points relevant to this discussion is presented. This theory ispresented to explain the observed alignment of a block copolymersolution in a flow field and in no way is intended to limit the scope ofthe invention.

The model used in the present discussion is shown in FIG. 4a for theeccentric cylinders system in which a cylinder 50 of radius R₁ lieswithin a larger cylinder 52 of radius R₂. A polymer solution 54 isassumed to be uniformly distributed laterally and to separate the twocylinders by a gap clearance equal to 2H which reaches a minimium of 2H,at a nip 56. Cylinders 50 and 52 rotate in the directions indicated byarrows 58. The cylinders 50 and 52 begin "biting" on the polymer at alocation x=X₂ upstream from the nip 56 and the polymer 54 remains inclose contact with both cylinders up to a detachment point x=X₁downstream from the nip 56. The locations of points X₁ and X₂ depend onthe radii, the viscosity and density of the solution and on its volume.For the system of FIG. 4a, the weight of the inner cylinder is also afactor. Using conventional methods, the shear and elongation/compressionrate and units in the fluid can be determined. Extremely large valuescan be obtained using the apparatus of the present invention. FIG. 4billustrates these parameters for the adjacent cylinders system shown inFIG. 1.

One of the additional characteristics of the present system is that thevelocity profile is not hilly developed. This results in an elongationalflow upstream and a compressional flow down stream from the nip. Thetotal number of shear and elongation/compression units experienced bythe material may be found by estimating the fraction of time in eachrotational cycle that the material is in contact with both rolls. InFIG. 4a, the fraction of time in each cycle in which the materialundergoes alignment in the contact zone from X₂ to X₁ will increase asR₁ approaches R₂. Hence, maximum orientation occurs with cylinder ofcomparable radii.

When the material in not in contact with the cylinders, it may undergostress relaxation. The extent to which the material relaxes may bereduced by rotating the cylinders at higher tangential velocities orpassing the material through several nips in a single cycle (as in FIG.2), thereby reducing the relaxation time between contacts. Althoughrelaxation may take place in between successive contact periods, thereseems to be no reason for any misalignment of molecules ormicrostructures to occur that have been previously aligned. Stress isalso expected to relax downstream from the nip in the compression zoneand may possibly be accompanied by some degree of misalignment. However,the combined effects of shear and compression in this region are unclearand the effects of compression may in fact be beneficial to the overallalignment.

The elongational component of the flow field is significant in achievingthe alignment of both the polymer molecules and, later, themicrostructures resulting from microphase separation. Whereas pure shearmay have a "tumbling" effect on the molecules and microstructure,elongational flow has the ability to realign and stretch them in flowdirection.

According to the invention, a typical oriented microphase-separatedblock copolymer structure is prepared in the following way. The methodis referred to hereinafter as roll-coating. A particular triblockcopolymer material used is a polystyrene-polybutadiene-polystyrene(PS/PB/PS) triblock copolymer with a butadiene centerblock of 58,000molecular weight and styrene endblocks of 11,000 molecular weight each(SBS 1158-11) with a nominal composition of 31% wt polystyrene. At thiscomposition, microphase separation is expected to form polystyrenecylinders in a polybutadiene matrix. A particular diblock copolymermaterial used is a polystyrene-poly(ethylene/propylene) diblockcopolymer stated by Shell Chemical Co. to have a nominal composition of37% wt. polystyrene.

Concentrated diblock and triblock solutions are made up as several ten'sof weight percent in a solvent such as toluene or cumene. Forconcentrations below the MST, the process is not dependent on theinitial staring concentration of the polymer solution. The concentrationis selected to obtain a workable viscosity below the point of microphaseseparation. Cumene is preferred as a solvent for thepolystyrene-polybutadiene system for two reasons. First, it is a lesspreferential solvent than toluene and is known to be non-selective forstyrene and butadiene blocks. Secondly, cumene has a lower vaporpressure than toluene which permits an even slower (and more controlled)rate of solvent evaporation. An aliquot of solution is introduced intothe nip area and flows continuously between the rotating cylinders. Asthe solvent is evaporated and the concentration of the solution rises,block copolymer microphase separation occurs and a film forms on anycylinder that is not coated or made from a high release material.According to the different embodiments, a typical PS/PB/PS solution isroll-cast on the order of several minutes to several hours, dependantupon the rate of solvent evaporation and the characteristics of theparticular polymer/solvent combination.

It is important to have control over the rate of evaporation. Slowevaporation allows maximal alignment to occur before the solutionreaches a critical concentration and the polymer freezes into its finalorientation. Use of a solvent-saturated environment is a useful way ofslowing down the rate of solvent removal during the critical processingperiod when the microdomains are forming in an aligned state. Solventcan be introduced above the cylinders in the gas flow field. Solventscan also be heated to further control evaporation. When all thecopolymer coats the cylinder surface, no liquid is observed in thesystem. At this point, the film may still contain a significant amountof solvent in the copolymer film. Warming the films is desirable todrive off the residual solvent. A cylinder equipped with a heater can beused for this purpose. Reduced-pressure evaporation can also be used.

Films in a wide range of thicknesses can be successfully cast. In orderto cast thicker films, a second portion of copolymer solution can beintroduced after first portion of copolymer solution has been treatedaccording to the invention. Additional copolymer solutions alternatelycan have a different composition so as to obtain a range of anisotropicproperties in the resultant oriented structure. The method overcomes thethickness limitations encountered in most of the prior art approachesmentioned above.

The anisotropy resulting from the uniform orientation of polystyrenecylinders throughout the sample is confirmed by small angle X-rayscattering (SAXS) observations. FIG. 5 is a 2-D SAXS pattern of atypical roll-cast film in which the path of the X-ray was parallel tothe orientation of the polystyrene cylinders. This figure indicates thatthe microstructure of the roll-cast films is not only highly orientedbut also approaches that of a single crystal with hexagonal symmetry.Additional support for the marked improvement in alignment of roll-castfilms is seen by comparison of the photographs in FIG. 6a and 6b. FIG.6a is a transmission electron microscopy (TEM) photomicrograph of a filmproduced according to a prior art method described above. FIG. 6b is aTEM photomicrograph of a film produced according to the presentinvention showing uniform arrangement of the cylinders in a nearsingle-crystal hexagonal array. A series of experiments was carried outaccording to the procedure described immediately above. A system similarto that illustrated in FIG. 1 was employed. The experimental conditions(relative proportion of polystyrene and polybutadiene, solvent andcasting time) are reported in Table 1, as well as the morphology of thefinal oriented structure and a qualitative assessment by SAXS of thedegree of alignment.

                  TABLE 1                                                         ______________________________________                                        Roll-casting conditions and degree of alignment                                                        casting                                                run solvent p/s.sup.1 time (min) structure.sup.2 alignment                  ______________________________________                                        1    cumene    1:2     120     cylinder                                                                              good                                     2 cumene 1:2 15 cylinder none                                                 3 chloroform 1:2 10 cylinder fair                                             4 cumene 1:2 30 cylinder good                                                 5 cumene 1:4 60 lamellae good                                                 6 cumene 1:2 100 cylinder.sup.3 good                                          7 cumene 1:2 120 spheres none                                               ______________________________________                                         .sup.1 ratio of weight polymer (g) and the volume of solvent (ml)             .sup.2 at equilibrium                                                         .sup.3 refers to structure of 90% component                              

Comparison of runs 1 and 2 shows the effect of roll-casting time. Asample roll-cast for two hours shows a high degree of alignment. Noalignment is found for the same composition roll-cast for 15 minutes andthen left to dry on a single rotating cylinder after increasing the nipso that there was no contact between the cylinders. Very little solventevaporated during the 15 minutes of induced flow and the concentrationof polymer was still below that of the microphase separation so thatthere were no domains to align.

Comparison of runs 2 and 3 shows that shorter casting times require ahigh vapor pressure solvent to obtain alignment. A 10 minute run usingchloroform was sufficient to reach microphase separation and topartially align the microdomains. However, rapid rate of evaporation didnot allow for complete alignment and the polystyrene cylinders losttheir mobility before the flow field could have its full effect. Use ofa chloroform-saturated environment would improve degree of alignment byslowing down the rate of evaporation.

Run 5 shows that other microstructures may be successfully oriented byroll-casting. Run 6 contains an additional 10% wt polystyrenehomopolymer and indicates that blends may also be aligned by rollcasting SAXS and TEM indicate that the homopolymer polystyrene hasphase-separated from the block copolymer into ellipsoidal domains andthat very little of the homopolymer exists in the PS-segment of themicrodomains. Run 7 indicates that, as expected, isotropicmicrostructures can not be aligned under the flow conditions. It islikely, however, that ellipsoids rather than true spheres may form underflow field conditions.

What is claimed is:
 1. An oriented block copolymer structure, saidoriented block copolymer having aligned microdomains therein wherebythere is a high degree of order and said structure is of near singlecrystal quality, said oriented block copolymer structure being a filmlayer further including at least one additional film of the same ordifferent block copolymers attached by reaction to said structure.
 2. Anoriented block copolymer structure, said oriented block copolymerstructure having aligned microdomains therein whereby there is a highdegree of order and said structure is of near single crystal quality,said oriented block copolymer structure further including at least oneadditional film of the same or different block copolymers attached bycrosslinking, said structure being made by the method comprising thesteps of:preparing a copolymer solution of at least one block typecopolymer; placing said copolymer solution in an apparatus which createsat least one flow field to orient polymers therein; evaporating solventmaterial from a film formed by said apparatus; treating of a prior filmto provide for crosslinking; repeating the first three steps to placeanother film upon said prior film; and removing said structure from saidapparatus.
 3. An oriented block copolymer structure as defined in claim2 wherein said structure is further defined by a 2-D small angle x-rayscattering pattern as shown in FIG. 5 and a transmission electronmicroscopy photomicrographs as shown in FIG.
 6. 4. An oriented blockcopolymer structure as defined in claim 1 wherein said structure isfurther defined by a 2-D small angle x-ray scattering pattern as shownin FIG. 5 and a transmission electron microscopy photomicrographs asshown in FIG.
 6. 5. An oriented block copolymer structure as defined inclaim 2 wherein said block copolymer is a PS/PB/PS triblock copolymer.6. An oriented block copolymer structure as defined in claim 1 whereinsaid block copolymer is a PS/PB/PS triblock copolymer.
 7. An orientedblock copolymer structure as defined in claim 2 wherein said film has ananisotropic elastic behavior on different perpendicular axes in a singlelayer.
 8. An oriented block copolymer structure as defined in claim 1wherein said film has an anisotropic elastic behavior on differentperpendicular axes in a single layer.